Phenolic novolak resin compositions containing 5-indanol and their use in radiation-sensitive compositions

ABSTRACT

A phenolic novolak resin composition comprising a condensation product of at least one aldehyde source with a phenolic source comprising 5-indanol. Said phenolic novolak resins are used in radiation-sensitive compositions, especially those useful as positive-working photoresists.

This application is a continuation of application Ser. No. 07/713,894,filed Jun. 12, 1991, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to selected phenolic novolak resins madefrom 5-indanol. Furthermore, the present invention relates toradiation-sensitive compositions useful as positive-working photoresistcompositions, particularly, those containing these phenolic novolakresins and o-quinonediazide photosensitizers. Still further, the presentinvention also relates to substrates coated with theseradiation-sensitive compositions as well as the process of coating,imaging and developing these radiation-sensitive mixtures on thesesubstrates.

2. Description of Related Art

Photoresist compositions are used in microlithographic processes formaking miniaturized electronic components such as in the fabrication ofintegrated circuits and printed wiring board circuitry. Generally, inthese processes, a thin coating or film of a photoresist composition isfirst applied to a substrate material, such as silicon wafers used formaking integrated circuits or aluminum or copper plates of printedwiring boards. The coated substrate is then baked to evaporate anysolvent in the photoresist composition and to fix the coating onto thesubstrate. The baked coated surface of the substrate is next subjectedto an image-wise exposure of radiation. This radiation exposure causes achemical transformation in the exposed areas of the coated surface.Visible light, ultraviolet (UV) light, electron beam and X-ray radiantenergy are radiation types commonly used today in microlithographicprocesses. After this image-wise exposure, the coated substrate istreated with a developer solution to dissolve and remove either theradiation-exposed or the unexposed areas of the coated surface of thesubstrate.

There are two types of photoresist compositions--negative-working andpositive-working. When negative-working photoresist compositions areexposed image-wise to radiation, the areas of the resist compositionexposed to the radiation become less soluble to a developer solution(e.g., a cross-linking reaction occurs) while the unexposed areas of thephotoresist coating remain relatively soluble to a developing solution.Thus, treatment of an exposed negative-working resist with a developersolution causes removal of the nonexposed areas of the resist coatingand the creation of a negative image in the photoresist coating, andthereby uncovering a desired portion of the underlying substrate surfaceon which the photoresist composition was deposited. On the other hand,when positive-working photoresist compositions are exposed image-wise toradiation, those areas of the resist composition exposed to theradiation become more soluble to the developer solution (e.g., arearrangement reaction occurs) while those areas not exposed remainrelatively insoluble to the developer solution. Thus, treatment of anexposed positive-working resist with the developer solution causesremoval of the exposed areas of the resist coating and the creation of apositive image in the photoresist coating. Again, a desired portion ofthe underlying substrate surface is uncovered.

After this development operation, the now partially unprotectedsubstrate may be treated with a substrate-etchant solution or plasmagases and the like. This etchant solution or plasma gases etch theportion of the substrate where the photoresist coating was removedduring development. The areas of the substrate where the photoresistcoating still remains are protected and, thus, an etched pattern iscreated in the substrate material which corresponds to the photomaskused for the image-wise exposure of the radiation. Later, the remainingareas of the photoresist coating may be removed during a strippingoperation, leaving a clean etched substrate surface. In some instances,it is desirable to heat treat the remaining resist layer after thedevelopment step and before the etching step to increase its adhesion tothe underlying substrate and its resistance to etching solutions.

Positive-working photoresists are generally prepared by blending asuitable alkali-soluble binder resin (e.g., a phenolic-formaldehydenovolak resin) with a photoactive compound (PAC) which converts frombeing insoluble to soluble in an alkaline aqueous developer solutionafter exposure to a light or energy source. The most common class ofPAC's employed today for positive-working resists are quinone diazideesters of a polyhydroxy compound. Typical novolak resins used today forpositive-working resins are made from various mixtures of ortho-cresol,meta-cresol, and para-cresol which are condensed with an aldehyde source(e.g., formaldehyde).

Positive-working photoresist compositions are currently favored overnegative-working resists because the former generally have betterresolution capabilities and pattern transfer characteristics.

Photoresist resolution is defined as the smallest feature which theresist composition can transfer from the photomask to the substrate witha high degree of image edge acuity after exposure and development. Inmany manufacturing applications today, resist resolution on the order ofone micron or less are necessary.

In addition, it is generally desirable that the developed photoresistwall profiles be near vertical relative to the substrate. Suchdemarcations between developed and undeveloped areas of the resistcoating translate into accurate pattern transfer of the mask image ontothe substrate.

Increased resolution has been noted in positive photoresist systemswhose novolaks possess a high degree of ortho-, ortho-bonding. The termortho-, ortho-bonding is used to refer to the location and positions ofattachment of the methylene bridge between phenolic nuclei. Thus, themethylene bridge which connects two phenolic nuclei which is ortho toboth phenolic hydroxyl groups is regarded as ortho, ortho.

It is thought that ortho, ortho-bonding increases the interactionsbetween phenolic hydroxyls in the novolak and the photoactive compoundin positive photoresists compared to positive photoresists containingnovolaks which lack a high degree of ortho, ortho-bonding in theirmicro-structure. Although the exact character of these interactions isspeculative, e.g., hydrogen bonding, van der Waals forces, and the like,there is a correlation between increased resolution and contrastobserved in these positive resists whose novolaks contain a high degreeof ortho-, ortho-bonding compared to positive resists whose novolakslack this high degree of ortho-, ortho-bonding.

The optimum number of ortho, ortho-bonds necessary for optimuminteraction between the PAC and the novolak not known. However, it isnoted that novolak resins which have a very high percentage of ortho-,ortho-bonding (e.g., a very high content of para-cresol in the novolak)appear to result in photoresists having scum (i.e., undesired residuesin the exposed and unexposed areas). Accordingly, having the optimumnumber of ortho, ortho bonds distributed properly may minimize oreliminate this scum problem.

U.S. patent application Ser. No. 07/713,891, entitled"Radiation-Sensitive Compositions Containing Fully Substituted NovolakPolymers" filed the same day as this application and assigned to thesame assignee, is directed to making and using novolak resins containinga mixture of selected monofunctional and difunctional phenolic monomerswith controlled ortho-, ortho-bonding. That U.S. patent application isincorporated herein by reference in its entirety. 5-Indanol is onespecies of one particular class of difunctional phenolic monomersdisclosed in that U.S. patent application. Besides being useful inmaking those particular fully substituted novolak resins, it is believedthat 5-indanol may be useful in making other novolak resins which arealso useful in radiation-sensitive compositions. Thus, the presentinvention is directed to making novolak resins in general from5-indanol.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a phenolic novolakresin composition comprising a condensation product of at least onealdehyde source with a phenolic source comprising 5-indanol.

Moreover, the present invention is directed to a radiation-sensitivecomposition useful as a positive photoresist comprising an admixture ofo-quinonediazide compound and binder resin comprising a condensationproduct of at least one aldehyde source with a phenolic sourcecomprising 5-indanol. The amount of said o-quinonediazide compound orcompounds being about 5% to about 40% by weight and the amount of saidbinder resin being about 60% to 95% by weight, based on the total solidcontent of said radiation-sensitive composition.

Still further, the present invention also encompasses the process ofcoating substrates with these radiation-sensitive compositions and thenimaging and developing these coated substrates.

Also further, the present invention encompasses said coated substrates(both before and after imaging) as novel articles of manufacture.

DETAILED DESCRIPTION

The phenolic resins of the present invention are made by reacting analdehyde source with 5-indanol alone or in combination with otherphenolic moieties under usual novolak-making conditions. Any suitablealdehyde source may be used for this reaction. Examples of aldehydesources include formaldehyde, acetoaldehyde, haloacetoaldehydes,benzoaldehydes, halobenzoaldehydes, and the like. 5-Indanol has thefollowing chemical structure: ##STR1##

Other phenolic moieties include phenol, cresols, xylenols,trimethylphenols, and the like may be mixed with the 5-indanol.

Generally, this reaction occurs in the presence of an acid catalyst.Suitable acid catalysts include those commonly employed in acidcondensation-type reactions such as HCl, H₃ PO₄, H₂ SO₄, oxalic acid,maleic acid, maleic anhydride, and organic sulfonic acids (e.g.,p-toluene sulfonic acid). The most preferred acid catalyst is oxalicacid. Generally, it is also preferred to carry out the condensationreaction of compounds in the presence of an aqueous medium or an organicsolvent. Suitable organic solvents include ethanol, tetrahydrofuran,cellosolve acetate, 1-methoxy-2-propanol and 2-ethoxy ethanol. Preferredsolvents are water-soluble solvents such as ethanol,1-methoxy-2-propanol and 2-ethoxy ethanol.

In making one preferred class of resins, the preferred precursors,namely, phenolic monomers (most preferably, a mixture of 5-indanol,meta-cresol and/or para-cresol), and formaldehyde are preferably placedin a reaction vessel. The reaction mixture usually also contains an acidcatalyst and solvent as noted above. The mixture is then Preferablyheated to a temperature in the range from about 60° C. to about 120° C.,more preferably from about 65° C. to about 95° C., for thenovolak-forming condensation polymerization reaction to occur. If anaqueous medium is used instead of an organic solvent, the reactiontemperature is usually maintained at reflux, e.g., about 90° to 100° C.The reaction time will depend on the specific reactants used and theratio of formaldehyde to phenolic monomers. The mole ratio offormaldehyde to total phenolic moieties is generally less than about1:1. Reaction times from 3 to 20 hours are generally suitable.

These preferred resins of the present invention preferably have amolecular weight of from about 500 to about 25,000, more preferably fromabout 750 to about 20,000. These preferred resins also have from about0.1 to 100, more preferably about 5 to 60, mole percent of 5-indanol.

The 5-indanol containing resins of the present invention may be mixedwith photoactive compounds to make radiation-sensitive mixtures whichare useful as positive acting photoresists. The preferred class ofphotoactive compounds (sometimes called radiation sensitizers) iso-quinonediazide compounds particularly esters derived from polyhydricphenols, alkylpolyhydroxyphenones, aryl-polyhydroxyphenones, and thelike which can contain up to six or more sites for esterification. Themost preferred o-quinonediazide esters are derived from2-diazo-1,2-dihydro-1-oxo-naphthlene-4-sulfonic acid and2-diazo-1,2-dihydro-1-oxo-naphthalene-5-sulfonic acid.

Specific examples include resorcinol1,2-naphthoquinonediazide-4-sulfonic acid esters; pyrogallol1,2-naphthoquinonediazide-5-sulfonic acid esters,1,2-quinonediazidesulfonic acid esters of (poly)hydroxyphenyl alkylketones or (poly)hydroxyphenyl aryl ketones such as 2,4-dihydroxyphenylpropyl ketone 1,2-benzoquinonediazide-4-sulfonic acid esters,2,4-dihydroxyphenyl hexyl ketone 1,2-naphthoquinonediazide-4-sulfonicacid esters, 2,4-dihydroxybenzophenone1,2-naphthoquinonediazide-5-sulfonic acid esters, 2,3,4-trihydroxyphenylhexyl ketone, 1,2-naphthoquinonediazide-4-sulfonic acid esters,2,3,4-trihydroxybenzophenone 1,2-naphthoquinonediazide-4-sulfonic acidesters, 2,3,4-trihydroxybenzophenone1,2-naphthoquinonediazide-5-sulfonic acid esters,2,4,6-trihydroxybenzophenone 1,2-naphthoquinonediazide-4-sulfonic acidesters, 2,4,6-trihydroxybenzophenone 1,2-naphthoquinonediazid-5-sulfonicacid esters, 2,2',4,4'-tetrahydroxybenzophenone1,2-naphthoquinonediazide-5-sulfonic acid esters,2,3,4,4'-tetrahydroxybenzophenone 1,2-naphthoquinonediazide-5-sulfonicacid esters, 2,3,4,4'-tetrahydroxybenzophenone1,2-naphthoquinone-diazide-4sulfonic acid esters,2,2',3,4',6'-pentahydroxybenzophenone1,2-naphthoquinonediazide-5-sulfonic acid esters, and2,3,3',4,4',5'-hexahydroxybenzophenone1,2-naphthoquinonediazide-5-sulfonic acid esters;1,2-quinonediazidesulfonic acid esters ofbis[(Poly)-hydroxyphenyl]alkanes such as bis(p-hydroxyphenyl)-methane1,2-naphthoquinonediazide-4-sulfonic acid esters,bis(2,4-dihydroxyphenyl)methane 1,2-naphthoquinone-diazide-5-sulfonicacid esters, bis(2,3,4,-trihydroxyphenyl)methane1,2-naphthoquinonediazide-5sulfonic acid esters,2,2-bis(p-hydroxyphenyl)propane 1,2-naphthoquinonediazide-4-sulfonicacid esters, 2,2-bis(2,4-dihydroxyphenyl)propane1,2-naphthoquinonediazide-5-sulfonic acid esters and2,2-bis(2,3,4-trihydroxyphenyl)propane1,2-naphthoquinonediazide-5-sulfonic acid esters. Besides the1,2-quinonediazide compounds exemplified above, there can also be usedthe 1,2-quinonediazide compounds described in J. Kosar, "Light-SensitiveSystems", 339-352 (1965), John Wiley & Sons (N.Y.) or in S. DeForest,"Photoresist", 50, (1975), MacGraw-Hill, Inc. (N.Y.). In addition, thesematerials may be used in combinations of two or more. Further, mixturesof substances formed when less than all esterification sites present ona particular polyhydric phenol, alkylpolyhydroxyphenone,aryl-polyhydroxyphenone, and the like have combined witho-quinonediazides may be effectively utilized in positive actingphotoresists.

Of all the 1,2-quinonediazide compounds mentioned above,1,2-naphthoquinonediazide-5-sulfonic acid di-, tri-, tetra-, penta- andhexa-esters of polyhydroxy compounds having at least 2 hydroxyl groups,i.e., about 2 to 6 hydroxyl 9groups, are most preferred.

Among these most preferred 1,2-naphthoquinone-5-diazide compounds are2,3,4-trihydroxybenzophenone 1,2-naphthoquinonediazide-5-sulfonic acidesters, 2,3,4,4'-tetrahydroxybenzophenone1,2-naphthoquinonediazide-5-sulfonic acid esters, and2,2',4,4'-tetrahydroxybenzophenone 1,2-naphthoquinonediazide-5-sulfonicacid esters. These 1,2-quinonediazide compounds may be used alone or incombination of two or more.

The proportion of the radiation sensitizer compound in theradiation-sensitive mixture may preferably range from about 5 to about40%, more preferably from about 10 to about 25% by weight of thenonvolatile (e.g., nonsolvent) content of the radiation-sensitivemixture. The proportion of total binder resin of this present inventionin the radiation-sensitive mixture may preferably range from about 60%to about 95%, more preferably, from about 75 to 90% of the nonvolatile(e.g., excluding solvents) content of the radiation-sensitive mixture.

These radiation-sensitive mixtures may also contain conventionalphotoresist composition ingredients such as other resins, solvents,actinic and contrast dyes. anti-striation agents, plasticizers, speedenhancers. and the like. These additional ingredients may be added tothe binder resin and sensitizer solution before the solution is coatedonto the substrate.

Other binder resins may also be added beside the resins of the presentinvention mentioned above. Examples include phenolic-formaldehyderesins, cresolformaldehyde resins, phenol-cresol-formaldehyde resins andpolyvinylphenol resins commonly used in the photoresist art. If otherbinder resins are present, they will replace a portion of the binderresins of the present invention. Thus, the total amount of the binderresin in the radiation-sensitive composition will be from about 60% toabout 95% by weight of the total nonvolatile solids content of theradiation-sensitive composition.

The resins and sensitizers may be dissolved in a solvent or solvents tofacilitate their application to the substrate. Examples of suitablesolvents include methoxyacetoxy propane, ethyl cellosolve acetate,n-butyl acetate. xylene, ethyl lactate, propylene glycol alkyl etheracetates, or mixtures thereof and the like. The preferred amount ofsolvent may be from about 50% to about 500%, or higher, by weight, morepreferably, from about 100% to about 400% by weight, based on combinedresin and sensitizer weight.

Actinic dyes help provide increased resolution on highly reflectivesurfaces by inhibiting back scattering of light off the substrate. Thisback scattering causes the undesirable effect of optical notching,especially on a substrate topography. Examples of actinic dyes includethose that absorb light energy at approximately 400-460 nm [e g., FatBrown B (C.I. No. 12010); Fat Brown RR (C.I. No. 11285);2-hydroxy-1,4-naphthoquinone (C.I. No. 75480) and Quinoline Yellow A(C.I. No. 47000)]and those that absorb light energy at approximately300-340 nm [e.g., 2,5-diphenyloxazole (PPO-Chem. Abs. Reg. No. 92-71-7)and 2-(4-bipenyl)-6-phenyl-benzoxazole (PBBO-Chem. Abs. Reg. No.17064-47-0)]. The amount of actinic dyes may be up to 10% weight levels,based on the combined weight of resin and sensitizer.

Contrast dyes enhance the visibility of the developed images andfacilitate pattern alignment during manufacturing. Examples of contrastdye additives that may be used together with the radiation-sensitivemixtures of the present invention include Solvent Red 24 (C.I. No.26105), Basic Fuchsin (C.I. 42514), Oil Blue N (C.I. No. 61555), andCalco Red A (C.I. No. 26125) up to 10% weight levels, based on thecombined weight of resin and sensitizer.

Anti-striation agents level out the photoresist coating or film to auniform thickness. Anti-striation agents may be used up to 5% weightlevels, based on the combined weight of resin and sensitizer. Onesuitable class of anti-striation agents is nonionic silicon-modifiedpolymers. One preferred one is TROYKYD 366 made by Troy Chemical Co.Schenectady, N.Y. Nonionic surfactants may also be used for thispurpose, including, for example, nonylphenoxy poly(ethyleneoxy) ethanol;octylphenoxy (ethyleneoxy) ethanol; and dinonyl phenoxypoly(ethyleneoxy) ethanol.

Plasticizers improve the coating and adhesion properties of thephotoresist composition and better allow for the application of a thincoating or film of photoresist which is smooth and of uniform thicknessonto the substrate. Plasticizers which may be used include, for example,phosphoric acid tri-(B-chloroethyl)-ester; stearic acid; dicamphor;polypropylene; acetal resins; phenoxy resins; and alkyl resins up to 10%weight levels, based on the combined weight of resin and sensitizer.

Speed enhancers tend to increase the solubility of the photoresistcoating in both the exposed and unexposed areas, and thus, they are usedin applications where speed of development is the overridingconsideration even though some degree of contrast may be sacrificed,i.e., in positive resists while the exposed areas of the photoresistcoating will be dissolved more quickly by the developer, the speedenhancers will also cause a larger loss of photoresist coating from theunexposed areas. Speed enhancers that may be used include, for example,picric acid, nicotinic acid or nitrocinnamic acid at weight levels of upto 20 percent, based on the combined weight of resin and sensitizer. Apreferred speed enhancer is TRISP-PA which has the chemical names:1-[1'-methyl-1'-(4'-hydroxyphenyl)ethyl]-4-[1',1'-bis-(4-hydroxyphenyl)ethyl]benzene or phenyl;4,4'-[1-[4-[1-(4-hydroxyphenl)-1-methylethyl]phenyl]ethylidene]bis.TRISP-PA has a Chemical Abstract No. (CAS-110726-28-8).

The prepared radiation-sensitive resist mixture, can be applied to asubstrate by any conventional method used in the photoresist art,including dipping, spraying, whirling and spin coating. When spincoating, for example, the resist mixture can be adjusted as to thepercentage of solids content in order to provide a coating of thedesired thickness given the type of spinning equipment and spin speedutilized and the amount of time allowed for the spinning process.Suitable substrates include silicon, aluminum or polymeric resins,silicon dioxide, doped silicon dioxide, silicon resins, galliumarsenide, silicon nitride, tantalum, copper, polysilicon, ceramics andaluminum/copper mixtures.

The photoresist coatings produced by the above described procedure areparticularly suitable for application to thermally grown silicon/silicondioxide-coated wafers such as are utilized in the production ofmicroprocessors and other miniaturized integrated circuit components. Analuminum/aluminum oxide wafer can be used as well. The substrate mayalso comprise various polymeric resins especially transparent polymerssuch as polyesters and polyolefins.

After the resist solution is coated onto the substrate, the coatedsubstrate is baked at approximately 70° to 125° C. until substantiallyall the solvent has evaporated and only a uniform radiation-sensitivecoating remains on the substrate.

The coated substrate can then be exposed to radiation, especiallyultraviolet radiation, in any desired exposure pattern, produced by useof suitable masks, negatives, stencils, templates, and the like.Conventional imaging process or apparatus currently used in processingphotoresist-coated substrates may be employed with the presentinvention. In some instances, a post-exposure bake at a temperatureabout 10° C. higher than the soft bake temperature is used to enhanceimage quality and resolution.

The exposed resist-coated substrates are next developed in an aqueousalkaline developing solution. This solution is Preferably agitated, forexample, by nitrogen gas agitation. Examples of aqueous alkalinedevelopers include aqueous solutions of tetramethylammonium hydroxide,sodium hydroxide, potassium hydroxide, ethanolamine, choline, sodiumphosphates, sodium carbonate, sodium metasilicate, and the like. ThePreferred developers for this invention are aqueous solutions of eitheralkali metal hydroxides, phosphates or silicates, or mixtures thereof,or tetramethylammonium hydroxide (TMAH).

Alternative development techniques such as spray development or puddledevelopment, or combinations thereof, may also be used.

The substrates are allowed to remain in the 1 until all of the resistcoating has dissolved from the exposed areas. Normally, developmenttimes from about 10 seconds to about 3 minutes are employed.

After selective dissolution of the coated wafers in the developingsolution, they are preferably subjected to a deionized water rinse tofully remove the developer or any remaining undesired portions of thecoating and to stop further development. This rinsing operation (whichis part of the development process) may be followed by blow drying withfiltered air to remove excess water. A post-development heat treatmentor bake may then be employed to increase the coating's adhesion andchemical resistance to etching solutions and other substances. Thepost-development heat treatment can comprise the baking of the coatingand substrate below the coating's thermal deformation temperature.

In industrial applications, particularly in the manufacture ofmicrocircuitry units on silicon/silicon dioxide-type substrates, thedeveloped substrates may then be treated with a buffered, hydrofluoricacid etching solution or plasma gas etch. The resist compositions of thepresent invention are believed to be resistant to a wide variety of acidetching solutions or plasma gases and provide effective protection forthe resist-coated areas of the substrate.

Later, the remaining areas of the photoresist coating may be removedfrom the etched substrate surface by conventional photoresist strippingoperations

The present invention is further described in detail by means of thefollowing Examples. All parts and percentages are by weight unlessexplicitly stated otherwise.

EXAMPLES 1-5 Novolak Preparation

The following general procedure was used to prepare five novolak resinswhich are described in detail in Tables I and II below.

The phenolic monomers indicated in Table I, formaldehyde and oxalic aciddihydrate catalyst, were placed in a 4-neck glass flask equipped withmechanical agitation, condenser, electric heating mantle thermometer,and temperature control (thermowatch) unit. Each reaction mixture washeated to reflux (95°-100° C.). Each reaction was allowed to proceed for12-19 hours at reflux temperature. The unreacted formaldehyde and waterwere removed by atmospheric distillation under a mild flow of nitrogenat temperatures between 100° C. and 170° C. This was followed by vacuumdistillation started at 170°-200° C. and continued to 230°-265° C.During the vacuum distillation, the remaining unreacted m-cresol and5-indanol were removed. The pure molten novolak was poured out of theflask into an aluminum tray under a nitrogen atmosphere at 180° C.

                  TABLE I                                                         ______________________________________                                        Novolak Reaction Conditions                                                                                     CH.sub.2 O/                                                           Formal- Phenolic                                                                             Oxalic                               Novo-                     dehyde  Molar  Acid                                 lak   5-Indanol m-Cresol  37%     Ratio  Added                                ______________________________________                                        1     100 gm    00        45.4 gm 0.75   1.0 gm                                     0.746 Mole                                                                              00        0.5595                                                                        Mole                                                2     100.5 gm  55.5 gm   71 gm   0.693  1.5 gm                                     0.75 Mole 0.514 Mole                                                                              0.876 Mole                                          3     62 gm     200 gm    131.3 gm                                                                              0.70   1.5 gm                                     0.463 Mole                                                                              1.85 Mole 1.62 Mole                                           4     90.7 gm   109.7 gm  96 gm   0.70   1.5 gm                                     0.677 Mole                                                                              1.015 Mole                                                                              1.184 Mole                                          5     50.4 gm   94.8 gm   76.2 gm 0.75   1.5 gm                                     0.376 Mole                                                                              0.877 Mole                                                                              0.94 Mole                                           ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        Novolak Composition, Yield, and Properties                                                             CH.sub.2 O/       SP                                 Novolak                                                                              5-Indanol                                                                              m-Cresol Phenolic                                                                             Yield T.sub.c                                                                            (°C.)                       ______________________________________                                        1      100      0        0.75   78.8  --   146                                2      59.3     40.7     0.693  70.4  4200 124                                3      20.0     80.0     0.70   77.3  5    125                                4      40.0     60.0     0.70   78.6  125  125                                5      30.0     70.0     0.75   78.4  29   140                                ______________________________________                                         Yield = Percent of product by weight based on total phenolics conversion.     SP = Softening point measured by ball and ring method, ASTM No. 06.03.        T.sub.c = The time, in seconds, required to completely dissolve one micro     coating of novolak resin using an 0.265 N developer solution of TMAH          (aqueous)*. The coatings are prepared by spin coating novolak solutions o     2inch silicon wafers and baking them in a convection oven at 100°      C. for 30 mins. The measurement of T.sub.c is carried out during              development using laser interferometry technique according to general         teachings described in Grindle and Pavelcheck, Test and Measurement World     May, 1986, pages 102 et seq.                                                  *This developer is commercially available from OCG known as OPRD262           developer.                                                               

EXAMPLES 6-11 Resist Formulations

Six resist formulations were prepared by dissolving the novolaks ofeither Examples 2 or 4, or both, a photo active compound (PAC), a speedenhancer (SE), and 0.07% by weight of a leveling agent (TROYKYD 366 madeby Troy chemical Co. of Schenectady, N.Y. in a solvent mixture of 70% byweight ethyl lactate and 30% by weight ethyl-3-ethoxy propionate. ThePAC used in all six formulations was prepared by reacting six moles of1,2-naphthoquinonediazide-5-sulfonlychloride with a one mole of a trimerphenolic compound. The trimer was produced by condensing two moles ofpyrogallol with one mole of 2,6-bis(hydroxymethyl)para-cresol. Theamount of PAC in all resist formulations was 18% by weight in the totalsolids. The speed enhancer (SE) used in some of these formulations is acompound known commercially as TRISP-PA purchased from Honshu ChemicalInd. Co., Ltd., Japan. The amount of SE is calculated by weight percentof the novolak plus SE added weight.

Table III describes the different formulations of the resist examples.Table IV describes certain properties of these resists.

                  TABLE III                                                       ______________________________________                                        Resist Formulation Examples                                                           Novolak               Novolak                                         Resist  Example  Blend Ratio  Blend T.sub.c                                                                        % SE                                     ______________________________________                                        6       4        --           125    0                                        7       2:4      1:1          650    0                                        8       2:4      1:1          650    8.4                                      9       2:4      1:1          650    17.7                                     10      2:4      2:1          l500   19.3                                     11      2        --           4200   20.0                                     ______________________________________                                    

                  TABLE IV                                                        ______________________________________                                                              Line/Space                                                      Photospeed    Resolution                                                                              Contrast                                      Resist  (mJ/cm.sup.2) (μm)   (Tan Θ)                                 ______________________________________                                        6       143           0.55      2.15                                          7       428           0.50      2.3                                           8       192           0.55      2.29                                          9       86            0.65      1.67                                          10      113           0.62      1.79                                          11      150           0.65      1.67                                          ______________________________________                                         Contrast = (Tan Θ) slope of curve relating log exposure and log         dissolution rate.                                                        

While the invention has been described above with reference to specificembodiments thereof, it is apparent that many changes, modifications,and variations can be made without departing from the inventive conceptdisclosed herein. Accordingly, it is intended to embrace all suchchanges, modifications, and variations that fall within the spirit andbroad scope of the appended claims. All patent applications, patents,and other publications cited herein are incorporated by reference intheir entirety.

I claim:
 1. A phenolic novolak resin composition comprising a condensation product of at least one aldehyde source with a phenolic source comprising 5-indanol and at least one unit of a phenolic monomer selected from the group consisting of phenol, cresols, xylenols, and trimethylphenols.
 2. The phenolic novolak resin of claim 1 wherein said phenolic monomer comprises units of meta-cresol, para-cresol, and mixtures thereof.
 3. The phenolic novolak resin of claim 1 wherein said 5-indanol represents about 5% to about 60% by moles of said phenolic novolak resin. 